It is known in the art to provide cardiac assistance by introducing a balloon into the thoracic aorta of a patient and causing the balloon to inflate during diastole and deflate during systole. An extracorporeal pumping unit inflates and deflates the balloon in coordination with the electrocardiogram (ECG), with a suitable neutral drive gas, such as helium. Electrocardiograph leads provide timing information, such as the R wave, to identify systole and a pressure sensor at the catheter tip provides arterial pressure waveforms. This information is used to time the inflation and deflation, and to assess the hemodynamic effects of the treatment. Intra-aortic balloons are disclosed, for example, in U.S. Pat. No. 6,468,200 to Fischi, and U.S. Pat. No. 4,692,148 to Kantrowitz, et al.
U.S. Pat. Nos. 4,685,446, 4,771,765 and 4,902,273 to Choy et al. describe various heart assist devices. The Choy patents define a balloon which is inflated at the very early stages of the systolic phase and as a consequence the energy exerted is destructive. The heart muscle and the balloon are working in opposite directions, thus leading to damage of the *muscle and reduced cardiac output due to physical obstruction of the left ventricular outflow tract The shapes of the Choy devices can unexpectedly cause unpredicted damage.
Advantage of the present invention device and related method and system is in the provision of a specifically shaped device that is inflated within the ventricle at the end of the slow ejection phase of the beating heart. This phase corresponds to the ascending part of the ECG-T wave of the heart. Therefore the energy exerted by the balloon is not contradicting the natural muscle power of the beating heart but only displacing the residual volume of blood and fluid (which are the direct consequence of heart failure) at the end of the muscle contraction. Further more, the balloon is not obstructing the normal ejecting phase of the heart as it does when inflated in early systolic phase as described in the Choy et al. devices.
Use of an intra-aortic balloon reduces the load on the left ventricle and raises aortic pressure to increase the blood flow to the coronary and carotid arteries. This can reduce the pulmonary capillary wedge pressure by approximately 20%, and can decrease aortic systolic pressure by 10% to 20%. Mean arterial pressure can increase by 30 to 40% secondary to enhanced diastolic blood pressure, and both cardiac output and stroke volume may experience a moderate increase.
An intra-aortic balloon may be indicated for several conditions, such as cardiogenic shock; as an adjunct to thrombolysis or percutaneous transluminal coronary angioplasty (PTCA) in acute myocardial infarction (AMI) to maintain vessel patency; prior to coronary artery bypass graft surgery in high risk patients; severe mitral regurgitation (mitral valve too loose); decompensated mitral stenosis (mitral valve too tight); as a bridge to transplant (if an organ is readily available); refractory congestive heart failure; mechanical complication of AMI, i.e., mitral regurgitation due to papillary involvement or ventricular septal defect; or unstable angina refractory to medical therapy.